The National Museum of Denmark (Nationalmuseet) is considered one of Europe's best museums and represents quite the value proposition in that admission is completely free. You'll find it in downtown Copenhagen, right next to the Strøget.

The museum's collection is immense, including artifacts from Danish pre-history and coin exhibits from ancient Greece and Rome. Some travelers recommend making more than one trip, in fact, so that you'll have time to see all there is to see. The National Museum is open Tuesdays through Sundays from 10 a.m. until 5 p.m. For more information, click here.